1. Field of the Invention
The invention relates to a rotation detector.
2. Description of the Related Art
A conventional rotation detector, which can accurately measure a rotation angle even in case of occurrence of axis shift, is known (e.g., see JP-A-2004-264137).
The rotation detector described in JP-A-2004-264137 includes a magnetic sensor for detecting a magnetic field which is generated by a disc-shaped magnet connected to a rotation axis, a storage portion for storing an output value outputted from the magnetic sensor, and an arithmetic portion for deriving a rotation angle of the rotation axis based on the output value outputted from the magnetic sensor. By the arithmetic portion, each rotation angle obtained by producing a first axis shift in the rotation axis and rotating it, which is outputted from the magnetic sensor, is stored as a data 1 in the storage portion, each rotation angle obtained by producing a second axis shift in the rotation axis and rotating it, which is outputted from the magnetic sensor, is stored as a data 2 in the storage portion, and corrected values of phase and amplitude are determined based on the data 1 and the data 2. This enables to determine the corrected value of the output value outputted from the magnetic sensor at the time of rotating the rotation axis.
However, according to the above-mentioned conventional rotation detector, there is a problem that only the corrected value of the output value from the magnetic sensor used for deriving the rotation angle is determined and it is not possible to detect how the axis shift with respect to the rotation axis occurs.